Can some girls be blind to Flirting?

There is a shy girl I know since 3 months, and when I say that "she is different" she did not take it as a complement but thought it in a negative way, later I somehow managed to get her understand that that is a complement and I tried to mean no other girl is like her...

Is it possible that she is blind to flirting? How will I deal with her?

BTW did I freak her out or something and can this be something negative?

She chatted to me that day asking for help in formatting her computer and installing Windows. Just like any other regular day chat, but this time she was asking me whether I am free or not. I said it's OK I can show her now... But then she again said if I am not free then I can go now and we can do it later. I replied back I will have lunch in 10 mins, and she said, OK she will remember that and take track of the time... This I didn't hear from her before, is that something negative?
Can some girls be blind to Flirting?
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